The biliproteins are a family of naturally occurring chromophores which are made up of linear tetrapyrrole derivatives covalently bonded to a protein residue. Representative examples include phytochrome (1), which functions as the "on-off" switch for photomorphogenesis in higher plants, and phycocyanin (2), which is commonly found in eucaryotic algae and serves as a light harvesting protein. In addition to promoting seed germination and flowering, (1) has also been implicated in the control of potassium uptake, chloroplast movement and water permeability in green plant metabolism, and it is of particular interest due to its photoreversible-photochromic behavior. However, although the structure of the physiologically inactive Pr form is now reasonably well understood, little is known about the structure of the photoactivated Pfr form. In part this is due to the difficulty of preparing suitable model systems utilizing the available synthetic methodology in this area. In this proposal we attempt to address this deficiency by exploring a novel, and potentially highly efficient, synthetic route to the biliproteins and related materials. The approach described is a convergent one which offers excellent opportunities for the control of both relative and absolute stereochemistry, and it should be readily adaptable to the synthesis of porphyrins, corrins, and other biologically important macrocycles.